Redwood City, California/Buildings Import

Goals

Import Redwood City, CA has released address and building outline datasets.

Schedule

John Novak leads the import and plans to complete the work by end of 2013.

Import Data

Background

Data source site: Data acquired directly form City of Redwood City GIS Department
Data license: In Progress
Type of license (if applicable):
ODbL Compliance verified: Unknown

OSM Data Files

The generated OSM files can be found at https://github.com/oldtopos/RedwoodCityCA

Import Type

This is an initial import of building and address city data. If the city releases substantial future updates, additional imports may be undertaken, presumably with manual conflation to preserve user edits.

Methodology is manual conflation via a JOSM layer (created from the RWC building outline and address files) with current OSM data downloaded into a separate JOSM layer.

Data Preparation

Tagging Plans

• building: yes
• redwood_city_ca:bldg_id: int
• redwood_city_ca:addr_id: int
• addr:housenumber
• addr:street
• addr:city

Address points that cannot be associated with a building polygon are imported as point features (nodes)

• redwood_city_ca:addr_id: int
• addr:housenumber
• addr:street
• addr:city

Changeset Tags

• Changeset Description: Redwood City Building Outlines and Addresses import
• Source: City of Redwood City CA 1013

Data Transformation

1. Load building shapefile file into PostGIS, convert kml column to geometry
2. Load address shapefile file into PostGIS, convert kml column to geometry
3. Join address points to building polygons
4. Extract PostGIS building table data, to shapefile via ogr2ogr, filtering for only polygonal geometries, including gid column named as redwood_city_ca:bldg_id. Join address points to buildings where proper containment exists.
5. Extract PostGIS address table data, to shapefile via ogr2ogr, filtering for address points not associated with a building.
6. Convert both shapefiles to .osm file using ogr2osm

Data Transformation Results

The generated OSM files can be found at https://github.com/oldtopos/RedwoodCityCA. Note that this is raw output from ogr2osm. Manual merging and cleanup of overlaps is executed in JOSM before uploading to OSM.

Data Merge Workflow

Team Approach

John Novak is importing the OSM file geometry manually.

Workflow

1. Open rwcbuildingswithaddresses.osm in JOSM (Building polys with addresses)
2. Open rwcunusedaddresses.osm in JOSM (Address points not associated with a building poly)
3. Select a block or set of blocks to be updated
4. Download the corresponding area from the OSM servers as a new layer
5. Select building outlines via JOSM search tool
6. Use manual inspection to look for features that overlap.
   • Toggle the OSM layer visibility to help spot overlaps.
   • Pay special attention to nodes that have building tags and existing schools (since they are frequently already mapped).
   • Make sure to delete buildings from the Palo Alto data when tags are copied from the import data to existing OSM data.
   • Copy selected outlines from rwcbuildingswithaddresses.osm layer and paste into downloaded OSM layer.
   • Merge address points not associated with buildings and manually merge to building polygons as appropriate.
   • Address points for commercial/retail and those that are not definitely associated with a building are left as address nodes
7. Commit the buildings into their own changeset.
8. Return to step 1.

Conflation

Since the OSM data is being hand-imported in manageable chunks, conflation with existing is handled manually in JOSM. I prefer existing OSM data and tags over the imported data. Existing address tags are merged with newly created building outlines.

QA

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